Rolls of light sensitive paper and film require light-tight packaging so that such rolls are not exposed to white or room light whereby the light sensitive characteristics of the rolls would be damaged. While such packaging must be light-tight, such packaging needs to facilitate the loading of the rolls in room light into cooperating apparatus which dispense or otherwise use the paper or film. Further, once positioned within the cooperating apparatus, the packaging must not adversely affect the ease of rotation of the roll during unwinding, and must not interfere with the roll if the web is re-wound back onto the roll.
U.S. Pat. No. 4,148,395, commonly assigned, discloses a package which includes a pair of flexible opaque end disks or covers attached to the ends of a core of the roll, and an opaque leader attached to a leading end of the length of paper or film forming the roll. A peripheral portion on each end disk is folded over and adhered to an edge of an underlying convolution of the leader. A layer of adhesive is provided on the underside of the peripheral portion prior to folding over. When the leader is pulled away from the packaged roll, the end disks tear circumferentially at the edge of the roll, such that the peripheral portion remains adhered to the leader. Since the folded over portions tend to crimp or fold unevenly, passages for light tend to be formed between the folded over portions and the leader, which can allow light to reach and damage the paper or film.
U.S. Pat. No. 5,526,930, commonly assigned, discloses a light-tight package for a roll of a length of web material. An opaque leader is wound around the roll and folded-over potions of an opaque tearable end disk is held in place by tearable adhesive tape strips. A portion on the leader is adapted to initiate a tear in the tearable tape, whereby pulling the leader, the tape tears, and the end disks tear circumferentially; the folded-over portions adhering to the leader when the leader separates from the roll. While the apparatus has achieved a certain level of success, dependent on the material selected for the end disks, a tear may not be readily initiated in the end disks, the end disks may not propagate the tear using a low force, and the end disks may not tear uniformly. In addition, the end disks may not tear cleanly; for example, if a paper layer is present, small fibers of material may occur at the point at which the end disk tears.
U.S. Pat. No. 5,133,171, commonly assigned, discloses a package which includes a pair of similar end disks and a leader. After a first convolution of the leader is wrapped on the roll, peripheral portions of the end disks are folded over the first convolution. A second convolution is then wrapped onto the roll to capture the folded-over peripheral portions between the first and second convolutions and to make the package light tight. Friction is relied upon to retain the folded-over portions between the convolutions of leader and no adhesive is used. However, the frictional engagement between the folded-over portions and the convolutions of the leader occasionally is not sufficient to prevent the folded-over portions from slipping at least partially free, thereby permitting entry of light and damage to the product. The requirement for a second full convolution also adds expense to the product and produces additional waste material for the customer.
Research Disclosure No. 22932 of May 1983 shows a package in which the end disks have the same diameter as the roll. A strip of adhesive tape is wrapped around each of the circumferential edges of an outer convolution of the leader and then folded over onto the end disk. The folded over portions of the tape strips tend to crimp or fold unevenly, so that passages for light tend to be formed between the folded over portions and the end disks, which can allow light to reach and damage the paper or film. Extra components, such as an enclosing bag, may be necessary to ensure light tightness.
U.S. Pat. No. 5,353,933 discloses a package in which a light-shielding leader with covers is connected to the end of a photosensitive strip of material. The leader is wound twice around the roll, and the side edges of the covers are inserted into the core and fixed by the insertion of a bushing into the core with pressure. A notch is formed in the covers to ensure and facilitate opening at the forward end of the covers. When the leader is drawn, a pulling force acts on the notch, and the covers are tom along adhesion outside boundaries. Once torn, the covers extend or fan outwards from the core, which may adversely affect the ease of rotation when unwinding the web material from the core, resulting in image disturbance if an image is applied during unwinding. In addition, the extended covers may fold over if the web is re-wound back onto the roll, causing scratching of the photosensitive material. Further, providing notches in the covers results in an extra manufacturing step, and may tend to form light passages.
Canadian Patent Application No. 2,124,969 discloses a package wherein the end face of the roll is covered by a cover element including an opaque flexible sealing disk, a flexible section, and a hub-shaped section. The flexible section presses the sealing disk against the end face of the film roll to make a lightproof closure. The flexible section includes incisions on the periphery. The flexible section may include perforations in the peripheral area to reduce the pull force required to unroll the package and to form a tear along a predetermined tear line. Such an arrangement provides a complex assembly, resulting in a plurality of manufacturing steps.